Vehicle brake pressure monitoring system an method

ABSTRACT

The present invention relates to a vehicle brake system, which has a brake reservoir, and utilizes a tire management system that is in communication with the brake reservoir and a vehicle operator. As a result of this configuration, the tire management system communicates brake reservoir pressure signals to the vehicle operator, so that the operator is made aware of any low pressure conditions, in the trailer, before trying to move the trailer.

RELATED APPLICATIONS

This application is a divisional application of and claims benefit,under U.S.C. §120, of U.S. patent application Ser. No. 11/116,768, filedApr. 28, 2005 now U.S. Pat. No. 7,415,869, which application isincorporated herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a system for monitoring the pressure ina vehicle brake system, while utilizing a tire management system. Moreparticularly, the present invention relates to a system and a method formonitoring the pressure in a vehicle brake reservoir, where a vehiclehas an attached trailer that utilizes an existing tire managementsystem.

BACKGROUND OF THE INVENTION

Those skilled in the art know that vehicles have a brake system (VBS),which, typically, has a brake reservoir for providing proper pressurelevels of fluid (such as, air or a hydraulic fluid) within the brakesystem. It is further known that some vehicles (for example, trucks andtractors that pull trailers) have a tire management system (TMS), whichuses pressurized air from a VBS reservoir to maintain pneumatic pressurein the vehicle tires. Often, the TMS is associated with a trailerattached to the vehicle.

Unfortunately, current vehicle air brake systems, with “spring brakepriority,” allow a vehicle operator to move the trailer, regardless ofthe pressure level in the VBS reservoir. Consequently, it is possible tooperate the trailer without adequate VBS reservoir pressure to stop thetrailer. Low VBS reservoir pressure may be caused by a number offactors, for example, a faulty spring brake valve or a significant,though not gross, leak in the reservoir itself. In other circumstances(such as in a multiple trailer application), VBS reservoir pressure maybe too low to hold off the spring brakes, resulting in overheatedbrakes.

Examples of relevant art involving a brake air pressure supply or VBSreservoir pressure are as follows. U.S. Pat. No. 4,593,954 to Campaninidescribes an air brake valve system. The air brake valve system has avalve cluster on the trailer responsible for filling and protecting thepressure in the air reservoir tank. The valve cluster has a low pressurewarning means in the tractor to warn the operator of low air reservoirtank pressure. The valve cluster comprises a mechanical system thatdetermines when the air reservoir tank pressure is too low.

U.S. Pat. No. 4,763,959 to Vandermotter provides for an electroniccontrol for a vehicle braking system. The system includes a supplyreservoir connected to the compressor of the vehicle. A pressure sensoris directly connected to the supply reservoir, which is connected to afront and a rear service reservoir. The front and rear service reservoireach have individual pressure sensors. These pressure sensors areconnected to an electronic control unit, which monitors these pressuresensors.

U.S. Pat. No. 4,877,294to Kuhn et al. teaches a tractor-trailer brakingsystem having an electric pressure transducer disposed to sense thepressure of compressed air in the pneumatic power supply. The pressuretransducer is mounted on the supply tank to sense the pressure inside ofthe tank. Kuhn also indicates that the transducer acts via electronicsto operate an alarm in the operator's compartment, should the sensedpressure increase above, or decrease below, a predetermined amount.

U.S. Pat. No. 5,172,958 to Sell discloses a similar air brake valvesystem to that in Campanini, discussed above, however, the disclosure inSell indicates three valve clusters can be used. A first valve clustercontrols the passage of compressed air from the emergency gladhandsupply line to the spring air brakes. A second valve cluster controlsthe filling and protection of the air reservoir tank. The third valvecluster eliminates compounding of the braking forces by the servicebrakes when the spring brakes have been applied.

U.S. Pat. No. 5,533,866 to Malecha teaches a pressurized air brakesystem for a vehicle comprising a first reservoir and a second reservoirconnected to an air compressor. The first and second reservoirs areconnected to a control system. The control system is also connected tothe compressor for actuating and disengaging the compressor in responseto air pressure levels in the first and second reservoirs. Malechaindicates that the reservoirs are connected to service brakes of thetandem and trailer, parking brakes, and wipers, however, othercomponents can also be connected to the reservoirs. Each reservoir has aswitch containing a pressure diaphragm. The diaphragms toggle betweenactivated positions and deactivated positions in response to airpressure changes in the reservoirs. Malecha also states thatmicroprocessors and air pressure sensors can be used to monitorreservoir air pressure and control the compression of air by the aircompressor.

U.S. Pat. No. 5,592,754 to Krieder et al. provides for a pressuretransducer connected to a reservoir to sense the pressure in thereservoir. The transducer provides an electrical signal indicative ofthe pressure in the reservoir to an electronic controller. Thecontroller uses the signal to control three different outputs: a lowpressure warning lamp, a compressor control solenoid and a purge controlsolenoid. Krieder teaches that the controller is designed to controlthese items in lieu of three separate mechanical units.

U.S. Pat. No. 6,079,436 to Delfs et al. discloses a pressure sensorconnected to an air supply line between a check valve and the compressedair container. The sensor communicates the sensed pressure to controlelectronics. The control electronics signal one of two pressureregulating valves. The valve is connected to an outlet valve that allowsair from a compressor to at least one compressed air consumer.

U.S. Pat. No. 6,682,459 to Knight teaches a vehicle brake compressed airsupply system having an electronic air charge controller (EAC) and afirst and a second pressure sensor. The first pressure sensor measuresthe pressure within a line connected to a supply reservoir. The pressurein the line is indicative of the pressure in the reservoir. The sensedpressure is sent to the EAC so that it can determine if the pressure inthe reservoir is below a pre-determined amount. If the pressure is belowthe pre-determined amount, a signal is sent to the engine to increaseRPM.

It would, however, be safer and economically advantageous for a vehicleto utilize a vehicle brake systems in conjunction with an existing tiremanagement system, to detect and warn the vehicle operator of low brakepressure conditions.

SUMMARY OF THE INVENTION

The present invention relates to a vehicle brake system, which has abrake reservoir that is in communication with a vehicle tire managementsystem, which has a transducer that is in communication with a vehicleoperator. As a result of this arrangement, the transducer communicatesbrake reservoir pressure signals to the vehicle operator so that thevehicle operator is aware of low brake pressure conditions in thevehicle.

Further advantages of the present invention will be apparent from thefollowing description and appended claims, reference being made to theaccompanying drawings forming a part of a specification, wherein likereference characters designate corresponding parts of several views.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatical illustration of a vehicle in accordance withthe present invention;

FIG. 2 is a schematic circuit in accordance with the vehicle of FIG. 1;and

FIG. 3 is a flow chart of the logic in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is to be understood that the invention may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings, and described in thefollowing specification are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions, directions or other physical characteristics relating to theembodiments disclosed are not to be considered as limiting, unless theclaims expressly state otherwise.

FIG. 1 is a diagrammatical illustration of a vehicle 10, which may be,for example, a truck or a tractor, with a vehicle brake pressure monitorsystem (VPM) 20 disposed therewith. As illustrated, the vehicle 10 hasan attached trailer 25. The vehicle 10 comprises a vehicle electroniccontrol unit 12 (ECU), which may be a part of an engine, and acompartment 15, where a vehicle operator would be located. The vehicle10 also comprises a warning device 16, which is in electricalcommunication with the ECU 12 by way of a first electrical line 17.

The VPM 20 comprises a brake reservoir 30 (provided on heavy duty trucktrailers) that is part of a vehicle brake system 35 (VBS), a pressureprotection valve 28, and a tire management system 40 (TMS). The TMS 40may be a tire management system already installed on the vehicle 10. TheTMS 40 is utilized to maintain a certain level of air pressure in thevehicle tires (not shown). The VBS 35 utilizes the brake reservoir 30 toassure that a level of air pressure is sustained and is available to theVBS 35 for proper braking of the vehicle 10. The pressure protectionvalve 28 is utilized in the VPM 20 to only allow air flow through theTMS 40 and then onto the tires, if the air pressure in the reservoir 30is above a pre-set pressure limit. This design prevents the TMS 40 fromdepleting pressurized air from the brake reservoir 30 at the expense ofthe safety critical vehicle brake system 35.

It should be appreciated that in the present invention the trailer 25 isnot required. In this embodiment, the truck or tractor, itself, wouldcomprise the VPM 20, the TMS 40, and the VBS 35 with the brake reservoir30. This embodiment, however, would function much the same as thatdescribed above for the embodiment with the trailer 25.

Again referring to FIG. 1, the TMS 40 comprises a first air line 27 thatprovides pressurized air from the brake reservoir 30 to a supplysolenoid 46. The supply solenoid passes the pressurized air to a secondair line 49. The air line 49 provides the pressurized air to, forexample, the tires for maintaining air pressure within the tires. Inturn, the air line 49 is connected to a pressure transducer 44, whichalready exists in the TMS 40.

It is a discovery of the present invention that an additional transduceris not required for communicating the pressure within the brakereservoir 30 to the ECU 12, since the existing transducer 44 may beutilized. In the present invention, the communicating of the pressurewithin the brake reservoir 30 is provided via a second electrical line47. The second electrical line 47 electrically communications betweenthe pressure transducer 44 and a controller 45 (a.k.a., tire managementelectronic control unit). The controller 45 would be disposed on thetrailer 25 (or truck/tractor) and then electrically communicate brakepressure signals and/or various warning signals to the vehicle ECU 12via a third electrical line 18.

It should be appreciated that the electronic control function providedby the controller 45 could be provided by a different controller (notshown) that might be disposed elsewhere on the trailer 25 (ortruck/tractor), or by the vehicle ECU 12 itself, and still remain withinthe spirit and scope of the present invention.

FIG. 2 illustrates a schematic circuit of the TMS 40, which comprisesthe first air line 27, a supply solenoid 46, a bleed air line 41, thepressure transducer 44, an exhaust valve 43, and a control solenoid 42.The first air line 27 has the supply solenoid 46 connected thereto. Thebleed air line 41 is connected to the first air line 27 but bypasses thesupply solenoid 46. The pressure transducer 44 is connected to thesecond air line 49 downstream of the supply solenoid 46, and the exhaustvalve 43 is downstream of the pressure transducer 44 on the second airline 49. The exhaust valve 43 is controlled by the control solenoid 42via control line 48, and the control solenoid 42 is connected to thefirst air line 27.

The air pressure (e.g., in pounds per square inch) in the brake airreservoir 30 is determined by sensing air pressure within the first airline 27 of the tire management system 40 with the pressure transducer44. The pressure transducer 44 provides an electronic signal based onthe monitored air pressure in the first air line 27. This electronicsignal is transmitted to the tire management electronic control unit 45of the vehicle 10.

The tire management electronic control unit 45 calculates an airpressure of the brake air reservoir 30 and then communicates acalculated air pressure signal of the brake air reservoir 30 to anoperator of the vehicle 10 (for example, by way of the ECU 12 on thethird electrical line 18, and then on to the warning device 16 in thevehicle compartment 15 by way of first electrical line 13). When thewarning is activated, it is optionally possible that a data link messageis generated (see FIG. 3 and the discussion below).

The warning device 16 may take, for example, the form of a pressure readout and/or lights to indicate the pressure levels. It is alsoconceivable to mount a warning lamp on the nose of the trailer 25. Thewarning devices 16 could be devices that are common in the art.

Illustrated in FIG. 3 is a flow chart of the logic of the presentinvention, where the brake reservoir 30 is in pneumatic communicationwith the tire management system 40. The pressure transducer 44 is inelectrical communication with the controller 45. The controller 45 isalso in electrical communication with the warning device 16 in thevehicle compartment 15, wherein the controller 45 begins a startinglogic sequence (Start). The controller 45 then determines if thepressure in the brake reservoir 30 is greater than a brake reservoirpressure limit (pounds per square inch, PSI) and, if so, the controller45 deactivates the warning device 16 and returns to the starting logicsequence.

If the pressure in the brake reservoir 30 is not greater than a brakereservoir pressure limit, the controller 45 determines if a vehiclespeed (information) signal is available. If the controller 45 does notdetermine that the vehicle speed signal is available, then thecontroller 45 activates the warning device 16 and returns to thestarting logic sequence.

The vehicle speed signals may be provided from the data link 18 (a.k.a.a third electrical line 18), from an anti-lock braking system (ABS)module (not shown) disposed on or near the trailer 25. The vehicle speedsignals may also be provided other sources (truck/tractor), which mayutilize a PLC4TRUCKS link (based on components available from IntellonCorporation), a radio frequency link, or an industry standard wired databus (like Society of Automotive Engineers J1708 or J1587). In addition,the TMS controller 45 could be modified to utilize a separate hardwiredspeed sensor (not shown).

If the controller 45 does determine that the vehicle speed signal isavailable, then the controller 45 determines if the vehicle speed isequal to zero and, if so, then the controller 45 returns to the startinglogic sequence. If the speed is not equal to zero, then the controller45 activates the warning device 16 and returns to the starting logicsequence.

In addition to the logic sequences detailed above, the instant inventioncan include additional criteria that are indicated in FIG. 3 formonitoring brake pressure, for example:

a) at various steps within the logic sequence, optionally broadcastbrake reservoir pressure and controller 45 decisions on the data link,

b) provide a logic sequence step that would allow a movement of thetrailer 25 at low speeds without providing a warning, but thencommunicate a warning if a certain vehicle speed threshold (for example,10 miles per hour) were to be exceeded,

c) utilize of a rate of change in a rising and/or a dropping of brakereservoir supply pressure to reduce annoyance warnings,

d) determine the engine 14 revolutions per minute (RPM), in place ofvehicle speed,

e) determine if the air compressor (not shown) is running, in place ofor in addition to determining the brake reservoir pressure,

f) incorporate timers (for example, a reservoir pressure timer) into anyof the logic sequence steps, before various actions or inactions wouldbe taken, and/or

g) utilize various speed and pressure sensors data to develop aProportional Integral Derivative (PID) algorithm for warning of low airsupply.

As a result of any of these added criteria or a combination thereof,control between the trailer 25 and ECU 12 could then be provided.

Additional efficiencies may be obtained when the TMS 40 is integratedinto a controller (not shown) associated with the ABS. In such anarrangement, the electronic control unit 45, for the TMS 40, wouldactually be an ABS controller, which would control the ABS and also theTMS 40. This would allow sharing of wheel speed information, data links,and other information that would be present on the various electricalcommunication lines within the truck, tractor, and/or trailer.

In accordance with the provisions of the patent statutes, the principlesand modes of operation of this invention have been described andillustrated in its preferred embodiments. However, it must be understoodthat the invention may be practiced otherwise than specificallyexplained and illustrated without departing from its spirit or scope.

1. A trailer brake system, comprising: a tire management system on atrailer, comprising a trailer tire management electronic control unithaving a trailer pressure transducer in communication with an air linein communication with a trailer brake reservoir on the trailer; whereinthe electronic control unit determines air pressure in the reservoirfrom electronic signals from the transducer by way of air pressure inthe air line; further wherein when the pressure in the trailer brakereservoir is less than a trailer reservoir pre-set pressure limit, theelectronic control unit prevents the tractor-trailer operator frommoving the trailer and prevents the supply of trailer brake reservoirpressurized air to trailer tires.
 2. The trailer brake system of claim1, wherein the electronic control unit broadcasts brake reservoirpressure and electronic control unit decisions on a data link.
 3. Thetrailer brake system of claim 1, further comprising a pressureprotection valve for only allowing air flow into the trailer tiremanagement system and onto the trailer tires, when the air pressure inthe trailer brake reservoir is above the pre-set pressure limit.
 4. Thetrailer brake system of claim 3, wherein the determination of thepressure in the brake reservoir includes a determination of whether areservoir timer has elapsed.
 5. The trailer brake system of claim 1,wherein a determination of the pressure in the brake reservoir includesa determination of a rate of change of a rising or a dropping ofpressure in the trailer brake reservoir.
 6. The trailer brake system ofclaim 1, wherein the electronic control unit is in electricalcommunication with a warning device.
 7. The trailer brake system ofclaim 6, wherein when the pressure in the trailer brake reservoir isgreater than the trailer reservoir pre-set pressure limit, theelectronic control unit deactivates the warning device.
 8. The trailerbrake system of claim 6, wherein when the pressure in the trailer brakereservoir is less than the trailer reservoir pre-set pressure limit andthe trailer speed is not equal to zero, the electronic control unitactivates the warning device.
 9. The trailer brake system of claim 8,wherein the determination of trailer speed includes determination ofengine revolutions per minute.
 10. The trailer brake system of claim 6,wherein when the pressure in the trailer brake reservoir is not greaterthan a trailer reservoir pre-set pressure limit and a trailer speedsignal is not available, the electronic control unit activates thewarning device.
 11. The trailer brake system of claim 6, wherein whenthe trailer speed is not less than a trailer speed threshold, theelectronic control unit activates the warning device.